/**
 * Copyright 2010 Neuroph Project http://neuroph.sourceforge.net
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.neuroph.core.transfer;

import java.io.Serializable;
import org.neuroph.util.Properties;

/**
 * Step neuron transfer function. y = yHigh, x > 0 y = yLow, x <= 0
 *
 * @author Zoran Sevarac <sevarac@gmail.com>
 */
public class Step extends TransferFunction implements Serializable
{

  /**
   * The class fingerprint that is set to indicate serialization compatibility
   * with a previous version of the class.
   */
  private static final long serialVersionUID = 1L;

  /**
   * Output value for high output level
   */
  private double yHigh = 1d;

  /**
   * Output value for low output level
   */
  private double yLow = 0d;

  /**
   * Creates an instance of Step transfer function
   */
  public Step()
  {
  }

  /**
   * Creates an instance of Step transfer function with specified properties
   *
   * @param properties 
   */
  public Step(Properties properties)
  {
    try
    {
      this.yHigh = (Double) properties.getProperty("transferFunction.yHigh");
      this.yLow = (Double) properties.getProperty("transferFunction.yLow");
    } catch (NullPointerException e)
    {
      // if properties are not set just leave default values
    } catch (NumberFormatException e)
    {
      System.err.println("Invalid transfer function properties! Using default values.");
    }
  }
/**
 * 
 * @param net
 * @return 
 */
  @Override
  public double getOutput(double net)
  {
    if (net > 0d)
    {
      return yHigh;
    } else
    {
      return yLow;
    }
  }

  /**
   * Returns output value for high output level
   *
   * @return output value for high output level
   */
  public double getYHigh()
  {
    return this.yHigh;
  }

  /**
   * Set output value for the high output level
   *
   * @param yHigh value for the high output level
   */
  public void setYHigh(double yHigh)
  {
    this.yHigh = yHigh;
  }

  /**
   * Returns output value for low output level
   *
   * @return output value for low output level
   */
  public double getYLow()
  {
    return this.yLow;
  }

  /**
   * Set output value for the low output level
   *
   * @param yLow value for the low output level
   */
  public void setYLow(double yLow)
  {
    this.yLow = yLow;
  }

  /**
   * Returns the properties of this function
   *
   * @return properties of this function
   */
  public Properties getProperties()
  {
    Properties properties = new Properties();
    properties.setProperty("transferFunction.yHigh", String.valueOf(yHigh));
    properties.setProperty("transferFunction.yLow", String.valueOf(yLow));
    return properties;
  }

}
